attribute vec3 aStep;

uniform float uTime;
uniform float uSize;

void main() {
    vec4 g_Position = vec4(position, 1.0);
    vec4 w_Position = modelMatrix * g_Position;

    //点坐标=向量*时间
    w_Position.xyz += aStep * uTime;

    gl_Position = projectionMatrix * viewMatrix * w_Position;
    gl_PointSize = uSize;
}